Tennis alleys or lanes are operated for player practice and the improvement of their game, with the objective of realistic ball delivery and efficient recovery of balls returned by the player. Prior art machines and installations for this purpose have been complex and cumbersome, they have required the storage of a large supply of balls, the acceleration means have been detrimental to ball life, and the automatic simulation of serve variations has not been altogether realistic. Therefore, it is a general object of this invention to realistically serve a small supply of tennis balls, delivering all worn balls substantially the same as new live balls, delivering said balls through a true ground stroke trajectory, and recycling all balls returned to the net.
The cost of operating full tennis courts is more than double that of half-courts; due to the added labor in retrieving balls and investment inventory in a large number of balls. Therefore, it is the half-court with which this invention is particularly concerned, or practice alleys where the player has an opportunity to develope good strokes, good footwork, and good habits by which he can correct and improve his game; or to warm-up before actual play, or simply to develope natural playing ability. To these ends it is an object of this invention to provide a tennis ball server and pick-up system that recycles a small supply of tennis balls, all without alteration to the tennis court or alley floor. With the present invention, there are no pits to dig and/or no downslope required, and elevated structures are avoided; a characteristic feature of the present invention being to serve the ball from beneath the net with moderate overspin and at a speed establishing a trajectory that permits the player to track the ball during the half-court journey; recognizing that the player reaction time is half that for a full court. In this manner the ball stays within the base line of the court to rebound in the manner of a natural serve.
High speed balls are emitted with substantial top spin so as to have a retarding effect on the rebound and which produces a rather "heavy" realistic ball at the base line of the court to challenge the experienced player. Conversely, the server can be adjusted to deliver a relatively slow low spin ball which is readily handled by the beginner, but with full court feel. In actual practice, for example, few players introduced to this server comment at all on the emission of balls from below the net, except upon the initial encounter; and it is this "below the net installation" of the server and controlled trajectory thereby within the base line that is most practical and characteristic of this invention.
There is a practical limit to how narrow or how wide a practice lane or alley can be, twelve feet being a minimum and twenty-four feet a practical maximum. Because of the cover texture on tennis balls, they resist rolling and require a slope ratio of about one to five, particularly when they group or bunch up. Consequently a minimum lane width is to be desired in order to reduce the rise from the court center to either side thereof which determines the transverse ball run elevation. Furthermore, an inclined berm is provided to receive ground balls having sufficient velocity to climb into the said ball run for retrieval. Although the berm ramp is at a substantial incline, the ball run inclines are minimized (1-5) and all of which remains below the net and/or partially receives the lower margin of the net, as shown. It is an object therefore to provide an installation that retrieves tennis balls to the center of the net, and a server that emitts these tennis balls from below the net.
Balls that are retrieved by the player and which properly pass over the net are stopped in the normal manner by a damping net in the form of a back drop that depends below the top of the playing net and over the transverse ball runs. In this way, all tennis balls that pass over the net or up and over the berm ramp become retrieved balls, and in practice the percentage of these balls is high with respect to the ability of the player.
The sequence of serve and the placement of rebound at the base line is unique with the present invention. Heretofore, programming for such purposes has been stereotyped and/or inflexible with respect to timing, trajectory, and direction. With the present invention these factors of time, trajectory, and direction are dissimilar so as to produce an unpredictable sequence of serve, not following a determinable pattern but rather a random sequence of indeterminable character. As will be described, the three factors are motor controlled and each functioning on a time base disassociated with the frequencies of the others. Consequently, there is no detectable serve pattern, since the phase proximity of the three dissimilar frequencies is unpredictable as a practical matter.